High pressure combustor having a catalytic air preheater

Abstract

A combustor for generating a mixture of steam and combustion gas is located downhole in an oil well, so that the mixture can be injected directly into the reservoir, to displace heavy oil from the reservoir. The combustion is built up in stages, with each stage supplying hot air to the following stage. The first stage comprises a catalytic heat exchanger, which preheats the incoming air. One side of the exchanger is coated with catalyst. On this side of the exchanger the preheated air burns a clean fuel, so that heat flows through the metal wall of the exchanger to preheat the incoming air. The heated air from the first stage is used to ignite and burn a heavy fuel such as crude oil, which is burned in the second stage and following stages.

What is claimed is: 
     
       1. A catalytic combustor for generating a mixture of steam and combustion gas downhole in an oil well, comprising: (a) a nest of three coaxial metal pipes that define inner and outer annular passages,   (b) the wall in the inner annulus being coated with catalyst,   (c) means for directing incoming air first through the central pipe, then through the outer annulus in the opposite direction, and then through the inner annulus in the first direction, and   (d) means for mixing fuel with the air after it has traversed the outer annulus and before it has traversed the inner annulus.   
     
     
       2. The combustor of claim 1, wherein the inner annulus contains a nest of fins having the shape of the involute of a circle, the fins being attached to both walls of the annulus, the fins being coated with catalyst. 
     
     
       3. The combustor of claim 2 wherein the outer annulus is traversed by a corrugated fin that oscillates between the walls of the annulus. 
     
     
       4. A catalytic combustor for generating a mixture of steam and combustion gas downhole in an oil well, comprising: (a) a nest of three coaxial metal pipes that define inner and outer annular passages,   (b) the walls of the inner annulus being coated with catalyst,   (c) means for directing a mixture of gaseous fuel and oxidizing gas first through the central pipe, then through the outer annulus in the opposite direction, and then through the inner annulus in the first direction.   
     
     
       5. The combustor of claim 4 wherein the inner annulus contains a nest of fins having the shape of the involute of a circle, the fins being attached to both walls of the annulus, the fins being coated with catalyst. 
     
     
       6. The combustor of claim 5, wherein the outer annulus is traversed by a corrugated fin that oscillates between the walls of the annulus.